Lesson objective: Use multiplication and addition to solve area problems.

This lesson helps to build fluency with calculating area. The area model is used here because it highlights the relationship between area and multiplication and addition. This work develops students' understanding that area relates to multiplication and addition and that knowledge can be used to solve real world problems involving area.

Students engage in Mathematical Practice 8 (look for and express regularity in repeated reasoning) as they make connections between the concept of area and its relationship to both multiplication and addition by calculating area by both multiplying side lengths as well as by repeatedly adding the number of square units in a given number of rows. Students also create and examine models that illustrate the relationship between the area of a rectangle and the length of its sides (or rows and columns).

**Key vocabulary:**

- addition
- area
- equation
- length
- long
- multiplication
- square units
- units
- unknown
- wide
- width

**Special materials needed:**

- grid paper
- square tiles